/Engine/Plugins/Experimental/Water/Source/Runtime/Public/WaterQuadTree.h
Walks down the tree and returns the tile height at InWorldLocationXY in OutWorldHeight. Returns true if the query hits an exact solution (either leaf tile or a complete subtree parent), otherwise false.
bool QueryTileBaseHeightAtLocation ( const FVector2D & InWorldLocationXY, float & OutWorldHeight ) const